All You Need to Know About Sapphires and Rubies

In the jewellery and gem world, after diamonds, people tend to think about rubies, sapphires, and emeralds. Sapphires and rubies are part of the same family – corundum. They offer beautiful, coloured alternatives to diamonds, are still robust enough on the Mohs scale, and gem quality stones are also rare making them highly desirable to consumers. In this blog, we explore the corundum family and give you some insight and knowledge that may help you when considering stones for your bespoke piece of jewellery.

What’s the difference between Sapphires and Rubies?

As ruby and sapphire are part of the corundum family, and have the same chemical make-up (aluminium oxide), how do you differentiate between them? In their purest state of aluminium oxide, they are colourless, but it is the chemical elements present at the time of the crystal formation that give them their colour.

So, what’s the difference between a ruby and sapphire? All red, gem quality corundum is called ruby and all other gem quality stones that are not red, are sapphires. When chromium replaces some of the aluminium in corundum, it makes it red and a ruby, and when the trace elements are iron and titanium and it’s blue, it’s a sapphire. Saturation and shade are determined by the concentration of various elements. For example, if there is more iron in the crystal, that makes the sapphire more yellow and more chromium, will make it pink. This is how sapphires come in an assortment of colours!

What makes it a Ruby and not a Pink Sapphire?

But when does a pink sapphire stop being a sapphire and become a ruby? It’s a tricky one! Generally, the hue, tone and saturation will dictate, but the predominant colour needs to be red. The red colour of the stone must fall within a certain range to be deemed ruby. If pink, purple or orange undertones are dominant then it becomes a sapphire. However, market culture and geography play a part too. Gems that would be considered pink sapphire in the UK and US are often classified and sold as rubies in some Asian countries. Working with an international clientele means this regional variation needs to be kept in mind!

Ruby – King of Precious Stones

Over the centuries, ruby has come to have legendary status. Ancient Sanskrit texts call ruby “ratnaraj”, meaning “King of precious stones”, but other beliefs were held too. From warriors believing rubies would make them invincible in battle, to rubies being used to cure digestive issues and blood disorders, but it is ultimately the beauty of the stone that has cemented its place as a sought-after gem. If you exclude Imperial Jade and some mystic natural diamond colours, ruby is the world’s most expensive gemstone!

Burma (or Myanmar as it is now) has been synonymous with fine-quality ruby for years. Some other sources for fine gem quality ruby are Mozambique, Thailand, Cambodia, Sri Lanka, Vietnam, and Kenya.

When it comes to colour and value, the two go hand in hand. A deep, pure, vivid red is the most expensive, but this colour is rare and even the finest ruby will be about 80% red with undertones of orange, pink, purple or violet. When it comes to an individual preference, it is of course subjective as to what’s best, but sticking with the ‘not too dark, not too light’ adage would serve a client well. Transparency and inclusions will ultimately affect the ruby’s colour as well.

An inclusion free ruby does not exist, and it is hard to find one of a good size and colour which is inclusion free to the naked eye. But inclusions should not be seen as problematic in general as they are what give the stone its uniqueness and character!

Heat treatment of rubies to enhance colour and clarity is normal and widely acknowledged amongst jewellery houses. However, other such treatment practices, such as lead glass filling, is not generally accepted as it’s an unstable treatment – meaning it could alter the look of the stone at a later stage. A heat-treated ruby will not change colour of fade over time.

Sapphire – Fancy that!

When you think of sapphire jewellery, probably one of the most iconic pieces is the engagement ring that was Princess Diana’s and now is on the finger of her daughter-in-law, Catherine, Princess of Wales. Moreover, Kings and queens in ancient Greece and Rome were convinced that blue sapphires protected their owners from envy and harm and the clergy wore sapphires to symbolise Heaven in the Middle Ages. This helped cement sapphires as ‘royal’ and special stone.

Sources of sapphires are vast and often the colour tells you where they originate from. A very dark blue sapphire is frequently associated with Australia whilst a lighter blue ‘Ceylon’ sapphire is deemed to be Sri Lankan. Cambodia, Kenya, Madagascar, Thailand, Vietnam, Pakistan, and India are other notable sources.

As mentioned, not all sapphires are blue and those that come in other colours are called fancy sapphires. They come in violet, green, yellow, orange, pink, purple and other hues in-between. They can even be grey, brown, or black and some possess the ability to colour change under different lighting. Hue, tone, and saturation are the key factors to describing ‘colour’ in gemstones. Hue is the base colour; tone is the gem’s relative lightness and darkness, and saturation is the intensity of the hue.

As fancy sapphires are generally less available than blue, and some colours are rare (like padparadschas sapphires which are an intense pinkish orange hue), especially in very small or very large sizes, they can be more expensive than their blue counterpart. However, the most highly valued sapphires are the silky, violetish blue to blue, in a medium to medium-dark tone, with a vivid saturation.

Again, like rubies, an inclusion free natural sapphire does not exist, but it is about finding stones where they do not detract from the overall look of the stone, like black inclusions or blemishes to the surface of the stone. Eye clean sapphires are most desirable and like diamonds, this clarity impacts price too. Heat treatment, again, is common and accepted as a method to improve colour and clarity.

Sapphires do possess two phenomena typical to them: asterism and colour change and both affect value. With star sapphires, the straighter the rays and the purer the blue, the more valuable the stone becomes. With colour change, a strong change is blue and purple between fluorescent and incandescent light, and the more obvious the change, the more costly the stone.

Hardness, Toughness and Stability – Why it’s Important

The durability of a gem is key for its’ everyday use in jewellery. Durability is reflected in three different ways, hardness, toughness, and stability. Hardness refers to a stones ability to resist scratching and chipping, toughness is the ability to resist cleavage and fracture, and finally, stability is the change of appearance of a gemstone over time.

The Mohs Scale reflects hardness and is often the benchmark that is used in reference to stone suitability. The good news is that corundum is at 9 on the scale, with diamond only above at 10. However, the scale is not linear, and diamond is still substantially tougher than sapphire and ruby! In terms of toughness and stability, corundum fairs well.

Luckily the corundum family are overall pretty durable which makes them ideal for everyday wear but with the caveat that, as with any gem, care should still be taken!

The only thing left…

With that quick rundown on corundum, the only thing left to do is decide on what colour you want! Sophie would love to help source beautiful, dazzling sapphires and rubies for any commissions you have in mind, engagement ring, earrings, pendants, bracelets, and milestone commemoration pieces! Get in touch to start your bespoke jewellery story.